1. Field of the Invention
The present invention relates to an actuator, and more particularly, to an actuator, an actuator structure including a structure in which a piezoelectric thin layer is layered on a diaphragm and an art related to a method of manufacturing same.
2. Description of the Related Art
Japanese Patent Application Publication No. 5-296713 discloses a structure of a cantilever type displacement element formed by layering a piezoelectric film and an electrode on a substrate, wherein a stress relieving layer is provided at least one of between the layers of an electrode and a piezoelectric film and between the layers of the electrode and the substrate, in order to improve repetition durability, while preventing cracking of the piezoelectric film, peeling away of the interface between the piezoelectric film and the electrode, warping of the front end, and the like.
Japanese Patent Application Publication No. 2003-217421 proposes a structure for a micro-machine switch used for switching a high-frequency signal, wherein micro-machine switch has a cantilever beam shape where a piezoelectric film serves as a drive section, in order to achieve high responsiveness, low power consumption, high reliability and long life.
Japanese Patent Application Publication No. 2008-42069 discloses a composition for a lead zirconate titanate (PZT: General Formula Pb (ZrxTi1−x)O3 (0<x<1)) type piezoelectric layer formed by vapor phase epitaxy, in which stress is controlled by forming an orientation control layer having compressive stress on the lower electrode side of the piezoelectric body, in order to improve the crystalline orientation of the piezoelectric layer and suppress cracking.
However, the stress relieving layer disclosed in Japanese Patent Application Publication No. 5-296713 only serves to relieve stress produced at the interface between layers and cannot fully suppress warping of the cantilever section. Furthermore, with the structure of a cantilever type displacement element disclosed in Japanese Patent Application Publication No. 5-296713, the drive force (one type of stress) occurring when the piezoelectric body is driven is absorbed by the stress relieving layer, and therefore the displacement efficiency is poor, and if it is sought to increase the stress relieving effect more than is necessary, then there is a possibility that the drive force produced by the piezoelectric body is not transmitted and the cantilever section is not displaced sufficiently.
In the switch structure disclosed in Japanese Patent Application Publication No. 2003-217421, since there is a possibility of warping of the cantilever beam due to stress, then it is deduced that production yield will be poor. Furthermore, in Japanese Patent Application Publication No. 2003-217421, no specific method of manufacture is described and further modifications are required in the manufacturing process in order to achieve this switch structure in a satisfactory manner.
In the composition disclosed in Japanese Patent Application Publication No. 2008-42069, when choosing the orientation controlling layer, it is necessary to select a layer which receives compressive stress from the piezoelectric layer. For example, in the case of a composition formed by layering a lower electrode layer, a piezoelectric layer and an upper electrode layer onto a silicone (Si) substrate, the material which receives the compressive stress is generally required to have a smaller coefficient of thermal expansion than the Si. However, general ceramics and metals have a higher coefficient of thermal expansion than Si. Therefore, the materials which can be used in the orientation control layer disclosed in Japanese Patent Application Publication No. 2008-42069 are limited.